The present invention relates to a developing apparatus used in an electronic copying arrangement to develop an electrostatic latent image formed on a surface of a photoconductive member.
Conventionally, a magnetic brush developing method, a cascade developing method, and a fur brush developing method are known as methods for developing an electrostatic latent image. A new developing method has been developed recently in addition to these conventional methods. According to this new developing method, a toner carrier member is disposed to oppose the surface of the photoconductive drum. This member has a number of strip electrodes, arranged at equal intervals thereon. A potential, which changes as a time function, is sequentially applied to strip electrodes to generate alternating electric fields therebetween. A nonmagnetic toner is shifted between the electrodes along the direction of the electrode array. In this case, the toner is moved upward toward the photoconductive drum, vibrates, and floats in the form of smoke-like particles. In this state, the toner is supplied to the photoconductive drum to develop the latent image into a toner image.
A developing method of this type has the following problem. When voltage is applied to electrodes, which do not correspond to the electrostatic latent image, the intensity of the electric fields is strong in the portion between the electrodes and becomes substantially zero at the center of the electrode. For this reason, the toner particles are shifted by a strong electric field in the portion between the electrodes. However, no electric lines of force act on the toner particles at the center of the electrode. As a result, the toner particles are stacked on the electrode. This toner stack interferes with toner feeding and reduces the toner transport efficiency.